1. Field of the Invention
The present invention broadly relates to thermal oxidation testing of jet fuel and, more particularly, is concerned with a heater block assembly which allows for fuel thermal degradation deposits to be formed on a flat surface during the testing.
2. Description of the Prior Art
A conventional method for measuring the high temperature stability of a gas turbine fuel subjects a test sample of the fuel to conditions which can be related to those occurring in gas turbine engine fuel systems. The fuel sample is pumped at a fixed volumetric flow rate through a heater after which it enters a precision stainless steel filter where fuel degradation products may become trapped. The heater contains a heated aluminum tube and the fuel sample flows along and in contact with the exterior of the heated tube during the test.
The essential data derived from the test are the amount of thermal degradation deposits on the aluminum heater tube, and the rate of plugging of the precision filter located just downstream of the heater tube. The test results are indicative of fuel performance during gas turbine operation and can be used to assess the level of deposits that form when liquid fuel contacts a heated surface that is at a specified temperature. Further details of the testing method may be gained by reference to a publication designated as Report No. 72-162 and entitled "Proposed ASTM Method of Test for Thermal Oxidation Stability of Turbine Fuels Utilizing Jet Fuel Thermal Oxidation Tester" by ALCOR Inc., 5420 Bandera Road, San Antonio, Tex. 78238, dated August 1972.
One problem associated with the existing test apparatus is that the fuel deposits which will be analyzed are formed on an exterior surface of the heated tube which has a cylindrical shape. Procedures required to carryout certain analytical chemistry methods are difficult to perform on deposits present on rounded surfaces. For example, in infrared analysis of deposits one needs to look at a flat area or region of the deposit to perform the analysis.
Consequently, a need exists for improvement of the test apparatus so as to facilitate and accommodate the performance of a broader range of analytical chemistry methods on the deposits resulting from the test.